1. Field of the Invention
This invention relates to a distance measuring method and an apparatus utilizing the method. More particularly, the invention relates to a multi-direction distance measuring method and apparatus which are suitable for a visual sensor for a self-running robot or an obstacle detecting sensor for an apparatus for preventing the collision of automobiles and which can optically measure at a high speed the distance to an object to be measured extending in multiple directions.
2. Related Background Art
One example of an apparatus required to measure the distance to a surrounding object over multiple direction is a self-running robot or an apparatus for preventing collision of automobiles.
Self-running robot, measure the distance to a surrounding object over multiple directions as the means for recognizion the surrounding environment, and the robot can then run while avoiding a collision with the object on the basis of the thus obtained distance information.
Apparatus for preventing the collision of automobiles, measure the distance to a surrounding object over multiple directions as the means for detecting an obstacle, and on the basis of the thus obtained distance information, a warning is given to the driver or a signal for stopping or decelerating the automobile is produced when the automobile has approached an object, such as other automobiles or a wall beyond a predetermined distance.
One well known method for the multi-direction distance measurement as described above, comprises directing an ultrasonic wave to an object to be measured, analyzing the ultrasonic wave reflected and returned by the object to be measured and finding the distance to the object to be measured.
However, with the method of this type utilizing a sound wave, measurement is difficult when the object to be measured is small, and there has also been the problem that the resolving power is relatively low; further the measurement of the distance to an object at a great distance requires much time.
On the other hand, a method of optically accomplish multi-direction distance measurement, has been proposed which comprises projecting a slit-like light beam onto an object to be measured, measuring the shape of the bright line on the surface of the object from a direction different from the direction of projection and finding the distance from the shape of the bright line by operation.
However, in this method, there is the problem that inputting of the shape of the bright line and the operation after that requires a relatively long time.